This year 2 coil packs have been changed on my 99 V8. I had a diagnostic test on the car and apparently the other 6 need changed.

How do I test which packs are good and which are bad?.
I have 4 of those gizmo's that you put on the plug between the HT lead and flashes when the engine is running, they worked on my X300 but.... to get to the S Type plug you have to partially strip down the engine

Could they be tested with a test meter on the 2 electrical terminals?.

 

I understand in practice you can sometimes tell they're NOT working but trying to test them is a mug's game. Those things you describe really don't cut it with today's ignition systems - though again, if they show a fail then it's a fail. They're likely to suggest a pass when it should be a fail, however.

 

As far as I can make out to test them on the car you need sophisticated equipment.
A laptop type screen that shows graphs and all sorts of things that are out of the home mechanics budget

I have replaced the other 6 packs and the car is running fine again

 

You did the best thing. For a home guy all we can really do is replace the coils.
Ford actually has a coil stress tester but even then not all the dealers have them.
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